Method for the evaluation of road classification in navigation systems

ABSTRACT

A method for rating road classifications in navigational systems using fixed average speeds input into the system, to be replaced by or, if necessary, supplemented with continuously corrected, i.e., updated speed values.

BACKGROUND INFORMATION

Although applicable to any information systems which involve rating ofspecific, time-variable system parameters, the present invention, aswell as its underlying problem definition, are clarified with referenceto a navigational system located on board an automobile.

Present-day navigational systems are essentially composed of thefollowing subsystems: digital map, computational module for automaticroute determination, position-finding device, system management,automotive sensor technology for recognizing vehicle movements, as wellas input unit and output unit for the operation and guidance system.

In navigational systems having route guidance, to calculate the travelpath, also referred to in the following as route, from the geographiccoordinate S, usually representing the vehicle position, to anothercoordinate Z, as the destination, which is usually specified by thelocation, road or intersection and, in some instances by otherinformation such as street number, one must rate (evaluate) the roads tobe traveled, to achieve an “optimal” route guidance in accordance with apredefined criterion.

If the user of the system chooses “short route” as optimal, for example,then the criterion “search for the shortest drivable route” isstipulated for the system to calculate a route. Usually, however, such astipulation (input) does not lead to an effective route guidance, forexample when it comes to many overland routes via country roads or inlarger cities having many “30 k.p.h. zones”.

For that reason, a “fast” connection from S to Z is often considered tobe optimal. In this context, “fast” means that for the routecomputation, the roads are classified by type, such as expressway,national highway, country road, etc. The individual road classificationsin related-art navigational systems are then assigned fixed averagespeeds, such as 100 km/h for superhighways, 80 km/h for nationalhighways, etc. The route computation is then set up to calculate a routehaving altogether a shortest possible driving time.

In addition, there is also information about the probable period of timeuntil the destination is reached. This can be output to the user of thesystem, whether it be as a time span or as an estimated time of arrival.

Navigational systems of this kind are, however, static with respect toexternal conditions. They do not take into account the actual averagespeeds which are driven and which can be reached on the route.Furthermore, systems of this kind are not able to incorporate the user'sdriving habits in the route planning. For these reasons, they usuallyonly provide imprecise information about the time until the destinationis reached.

In addition, such a static assignment of average speeds to specific roadsections often results in longer routes than a system user would desireor would select if he/she were to use a road map. Moreover, depending onthe average speeds selected, the routes calculated by the system areoften characterized by an unjustified preference for major roads, suchas superhighways or national highways.

SUMMARY OF THE INVENTION

The method of the present invention has the advantage that, following acertain “transient recovery time”, (“response time”) the routecalculation is able to generate better routes for the most frequentlydriven surrounding area. In most cases, this is associated with ashorter driving time. In addition, the routes calculated by the systemare better adapted to the user's individual driving behavior. As aresult, the time needed to reach a destination, as queried of the systemor output by the system, is more accurate.

An idea underlying the present invention is for the above described,static rating of the road classifications using fixed average speedsinput into the system, to be replaced by or, if necessary, supplementedwith continuously corrected, i.e., updated speed values. In other words,instead of the fixed and invariably predefined road-classificationspeeds of the related art, actually reached speeds learned by the systemduring vehicle operation are, to an extent, used as a basis for routeplanning and estimating arrival time, etc. Because such averagedriving-speed values learned by the system are stored in a non-volatilememory, they are also available for a new route planning after thesystem is turned off.

For this, the information available during the driving operation,pertaining to the currently driven road classification and speed, isrepeated, for instance at intervals of one second or longer, and setagainst one another, separately for each road classification. As astarting value for such a calculation, one may use, for example, thefixed average speed indicated above, or alternatively thereto, a speedto be entered by the driver into the system.

Thus, in accordance with the general aspect of the present invention, adynamically adapted average value of the vehicle speed is used forcalculating the route for one or more partial sections K of a particulardriven road. The corresponding linking of database fields implemented inthe navigational system is, therefore, also dynamic. The system adaptsitself to the actually existing conditions.

In accordance with one preferred embodiment, a filtering takes placeover time, in order to recalculate the average vehicle-speed value thatis relevant to the rating. Such a filtering constitutes an especiallysimple implementation. In principle, however, other algorithms are alsopossible.

Another preferred embodiment provides for weighting the influence ofthis adaptation, variably, with respect to the recalculation. This makesit possible to minimize the effects of a “self-learning process” of thenavigational system on the stored attribute values for the average speedof a particular road section K. This can be useful in the event ofsnowfall or other adverse weather conditions, so that rare, exceptionalevents do not become the basis of a self-learning process for thenavigational system. In one simple variant, the user may choose, forexample, between heavy, average, and weak weighting. Alternatively,other weighting factors may also be input by the user.

For this, the following schema is given:

When v(tO,K) is the fixed average speed preset for road classification Kat the first system start-up; v(tn,K) is the adapted average speedcalculated for road classification K at instant tn; v(tn+1) is theinstantaneously driven speed and x the weighting factor, with which theold value in the particular case is linked to the new value, then, atinstant tn+1, the instantaneously adapted average speed is obtained forK as

v(t _(n+1) r,K)=(1−x).v(t _(n) ,K)+x.v(t _(n+1)).

In this context, it does not matter whether the road classifications areactually rated in the “km/h” unit; what is important is the change inratings as a function of values which are actually attained.

To be able to continue to use the values calculated within one drivingcycle later on, provision is made to store them in a non-volatilememory.

Likewise provided is the introduction of upper and lower limits for eachof the learned speeds; generally, this is more likely to result inunfavorable route proposals, for example, if the rating of an expresswaywere lower than that of a country road.

In accordance with another preferred embodiment, the method of thepresent invention may be improved by undertaking a separation into aso-called short-term and long-term adaptation, including different timeconstants and/or weightings xshort and xlong, respectively: the case ofshort-term adaptation, the intervals between tn and tn+i lie in theseconds range, and, in the case of long-term adaptation, in the minutesrange. In accordance with this separation, the driven speed may becalculated within the selected period of time. The above-mentionedweighting factor x may also be selected to be greater or smaller,depending on whether it is practical to give the active speed value agreater or smaller influence in the recalculation of the average value.The values from the long-term adaptation are preferably used for theroute calculation, and those from the short-term adaptation are used forupdating the time indication until the destination is reached.

In accordance with another preferred embodiment, a starting value may beproposed by the system user for recalculating the average value that isrelevant to the rating, and be entered by him/her into the system. Thismakes the system more flexible in its response to individual drivinghabits and to the configuration of individual road sections.

In accordance with another preferred embodiment, the method of thepresent invention may be simplified by an adaptation, without explicitconsideration of the road classifications, only with respect to theaverage vehicle speed, including appropriate percentage increase ordecrease in the rating factors of the individual road classifications.The average vehicle-speed value is then calculated on the basis of thecurrent average vehicle-speed value, and the weighting of roadclassifications, preset by the system, loses influence. A measure ofthis kind likewise enhances the flexibility of the navigational system.

Another preferred embodiment provides for the user to be given avariably adjustable way to influence route proposals generated by thesystem, in order to minimize or eliminate the influence of valueslearned by the system. The method of the present invention may besupplemented in this manner using statistics pertaining to the length ofthe calculated routes and analysis thereof. when the user drivesfrequently in the neighborhood of his/her residence, for example in acongested area, then, due to increased traffic volume, such as rush-hourtraffic, the adapted values are more likely to become low for the roadclassification rating. When the intention is to calculate a route to amore distant destination, it can then happen, under unfavorableconditions, that an inexpert route selection is made, for example, dueto strong consideration of minor roads. In such a case, given suchatypical destination distances, it would be more beneficial, forexample, for part of the adaptation to be carried out by overriding thevalues learned by the system, towards starting values acquired fromlong-term experience or preset by the user.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are illustrated in thedrawings and are elucidated in the following description.

FIG. 1 shows a detail of a vehicle's navigational system includingelements important to the present invention.

FIG. 2 shows a schematic block diagram including the steps of importanceto the present invention, during travel, in accordance with a preferredexemplary embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a detail of a vehicle's navigational system includingelements important to the present invention.

A processor 10 is linked to an input device 12 for inputting startingand destination locations, as well as for inputting other data. Anoutput for the driver may follow optically and acoustically via anoutput device 14. This essentially includes a display and associatedspeakers.

In addition, processor 10 is connected to a memory 16. Processor 10 hasread/write access to memory 16. Memory 16 is advantageously set up as anon-volatile memory. As described in greater detail below, it isintended for values of the instantaneous average vehicle speed, updatedduring travel, to be read out of this memory, and new values are to bewritten into it.

In addition, processor 10 is connected via an averaging unit 18 to themotor vehicle's speed signaling device 20. By way of the averaging unit,which may be a suitable, related-art logic circuit having integratingaction, active, instantaneous speed values are read off from speedsignaling device 20 and, following appropriate time intervals, combinedto form an arithmetic, i.e., integrated average value that is ofsignificance to the particular time interval.

FIG. 2 shows a schematic block diagram including the steps of importanceto the present invention, during travel, in accordance with a preferredexemplary embodiment.

In a step 200, the user starts the system and, in a step 205, allows thesystem to determine road classification K. He/she may then enter thedestination.

In accordance with the preferred functional sequence of the exemplaryembodiment, as illustrated in FIG. 2, method steps for a specific roadsection K, treated as a unit, are repeated in an outer loop, whose loopbody begins after step 200 and ends at decision 240. The averagedriving-speed values are repeated at specific instances tn, n=0, 1, 2 .. . This repetition is shown in the inner loop, beginning with step 215and ending with step 240.

In step 210, n is set to 0, and all values specific to road section K(section of the driven road classification) are read in from thenavigational system's database, in order to initialize all quantitieswhich are important to the method. In a further step 215, n is increasedby 1.

At the first pass through the inner loop, in a step 220, theabove-mentioned starting value for the average speed is read out ofmemory 16. Subsequently, in a step 225, the average speed value presentin averaging unit 18, which is based on the actually just driven speedspecifications (data) from speed signaling device 20, is recorded byprocessor 10.

Average vehicle-speed value v(t_(n+1),K), which is decisive for therating, is subsequently calculated in accordance with the followingformula:

v(t _(n+1) r,K)=(1−x).v(t _(n) ,K)+x.v(t _(n+1)).

This newly calculated value is then stored as an updated value in memory16, in step 235, and may now be used by the system for routecalculations and/or to indicate the probable arrival time at thedestination.

It is quite evident that, after one single pass through the inner loop,this newly calculated value is still not accurate enough. It is thendetermined in a step 240, whether the motor vehicle is still located onthe same partial section or road section K. If this is not the case, thesystem loops back to step 215, and the method is continued, followingthe same sequence,—assuming a normal travel characteristic—the valuestored in memory 16 becoming more and more realistic with everypass-through.

If this is not the case, preparations are made to be able to process thenext partial section K. Depending on the navigational system'simplementation method, the values relevant to this partial section K areread out of the database, and the system loops back to step 205. Themethod is then continued for this partial section, following the sameprinciple.

The method ends with the switching off of the system.

The inner loop may preferably be passed through relatively often, perminute. Preferred values lie within an interval of between 60 times perminute and two times per minute.

The outer loop is repeated as many times as there are different roadsections K on the route.

In the following, the advantageous effect of the method of the presentinvention is demonstrated on the basis of an exemplary calculation for asection from S to Z, it being possible to cover the section via twoalternative routes.

Route A includes a 10 km country road (assumed average speed v(tO,county road) =60 km/h), 80 km of expressway (100 km/h), and, again, of10 km county road.

The alternative route B includes, altogether, 30 km of county road and60 km of national highway (80 km/h).

Given fixed average speeds, this yields route A over the expressway(fast route), which is, however, 10 km longer than route B:

Route A 20 km county road 20 min 80 km expressway 48 min 68 min Route B20 km county road 30 min 60 km national highway 45 min 75 min

The road classification rating in accordance with the given exemplaryembodiment is now able to distinguish among different cases:

The user frequently drives in an area and at a time of day in which theexpressway is usually congested; the average speed is “learned downward”to 80 km/h; therefore, the path via the national highway proves to bethe better route:

Route A 20 km county road 20 min 80 km expressway 60 min 80 min Route B20 km county road 30 min 60 km national highway 45 min 75 min

Even when the national highways driven at average speeds appear to befaster than expected (95 km/h), the rating, altered by adaptation, leadsto route B, even though the advantage is minimal in this example.

Route A 20 km county road 20 min 80 km expressway 48 min 68 min Route B30 km county road 30 min 60 km national highway 37 min 67 min

If the system user prefers a speedy style of driving and if availableexpressways are found—the average speed is raised to 120 km/h —, theerror at the 11% level in the route's time indication is compensatedthrough adaptation of the road's rating:

Fixed values 20 km county road 20 min 80 km expressway 48 min 68 minAdapted values 20 km county road 20 min 80 km expressway 40 min 60 min

The short-term adaptation mentioned and described above is able tocorrect the time indication in the event of traffic jams even moreeffectively and make the adaptation to the prevailing road condition.

Although the present invention is described above with reference to apreferred embodiment, it is not limited thereto, but instead may bemodified in a variety of ways.

For example, the frequency with which the inner loop is passed throughmay be adapted to the navigational system's computing capacity. Inaddition, other mathematical algorithms may be employed to providevalues which are usable to the system from the multiplicity of averagespeed values read in from the speed signaling device via theaverage-value generator. In this case, various filter functions may beuseful.

In addition, the system may be equipped in a practical manner with anadditional option which allows one to temporarily discontinue with themethod of the present invention and, instead, to revert to standardroad-classification rating values present in the system. Here, thebenefit is derived that the system does not learn “incorrectly”, forexample, when the driver stops somewhere along the route to purchasesomething, or if he/she makes some other kind of atypical intermediatestop.

When the vehicle is turned off (ignition off), the navigational unit isusually switched off and/or is set to a stand-by mode. A temporarymethod for switching off the unit may also be provided during operationas a towing vehicle (towing, trailer towing).

What is claimed is:
 1. A method for rating road classifications in avehicle navigational system, comprising: assigning an averagevehicle-speed value to at least one partial section of a particulardriven road, for rating purposes; and performing a recalculation and anupdating of the average vehicle speed value relevant to the rating,during travel, at repeated instants in accordance with actually reachedspeeds.
 2. The method according to claim 1, further comprising:filtering, for the recalculation, over time for the averagevehicle-speed value relevant to the rating.
 3. The method according toclaim 1, further comprising: variable weighting an influence of anadaptation of the recalculation.
 4. The method according to claim 1,further comprising: displaying an arrival time at a destination using ashort-term adaptation, including a low time constant, wherein therecalculation of the average vehicle-speed value takes place using along-term adaptation, including a larger time constant.
 5. The methodaccording to claim 1, further comprising: proposing, by a system user, astarting value for the recalculation of the average value relevant tothe rating.
 6. The method according to claim 1, further comprising:using an active average value as a base quantity; and accounting fordifferent road classifications using percentage changes for therecalculation of the average vehicle-speed value.
 7. The methodaccording to claim 1, further comprising: giving a user a variablyadjustable way to influence route proposals to be generated by thesystem, in order to reduce an influence of values learned by the system.8. A method for rating road classifications in a vehicle navigationalsystem, comprising: assigning an average vehicle-speed value to at leastone partial section of a particular driven road, for rating purposes;adapting the average vehicle-speed value relevant to the rating, duringtravel, at repeated instants in accordance with actually reached speeds,through a recalculation; and filtering, for the recalculation, over timefor the average vehicle-speed value relevant to the rating.
 9. A methodfor rating road classifications in a vehicle navigational system,comprising: assigning an average vehicle-speed value to at least onepartial section of a particular driven road, for rating purposes;adapting the average vehicle-speed value relevant to the rating, duringtravel, at repeated instants in accordance with actually reached speeds,through a recalculation; and variable weighting an influence of anadaptation on the recalculation.
 10. A method for rating roadclassifications in a vehicle navigational system, comprising: assigningan average vehicle-speed value to at least one partial section of aparticular driven road, for rating purposes; adapting the averagevehicle-speed value relevant to the rating, during travel, at repeatedinstants in accordance with actually reached speeds, through arecalculation; and displaying an arrival time at a destination using ashort-term adaptation, including a low time constant; wherein therecalculation of the average vehicle-speed value takes place using along-term adaptation, including a larger time constant.
 11. A method forrating road classifications in a vehicle navigational system,comprising: assigning an average vehicle-speed value to at least onepartial section of a particular driven road, for rating purposes;adapting the average vehicle-speed value relevant to the rating, duringtravel, at repeated instants in accordance with actually reached speeds,through a recalculation; and proposing, by a system user, a startingvalue for the recalculation of the average value relevant to the rating.12. A method for rating road classifications in a vehicle navigationalsystem, comprising: assigning an average vehicle-speed value to at leastone partial section of a particular driven road, for rating purposes;adapting the average vehicle-speed value relevant to the rating, duringtravel, at repeated instants in accordance with actually reached speeds,through a recalculation; and using an active average value as a basequantity and taking into account different road classifications usingpercentage changes, for the recalculation of the average vehicle-speedvalue.
 13. The, method according to claim 1, further comprising: givinga user a variably adjustable way to influence route proposals to begenerated by the system, in order to reduce an influence of valueslearned by the system.
 14. A method for rating a road classification ina navigational system in a motor vehicle, comprising: assigning anaverage vehicle-speed value of the motor vehicle to at least one partialsection of a particular road being driven on by the motor vehicle;adapting an average value of a vehicle speed relevant to a rating duringtravel by recalculating at repeated instants according to an actuallyreached speed; and rating the average vehicle-speed for the roadclassification of the particular road being driven on by the motorvehicle.
 15. The method of claim 14, wherein the road classificationsinclude at least one of a country road, an expressway, a rural route, afederal highway, an interstate highway and a state route.